Arctic melting may help parasites infect new hosts

Grey seals are encountering a killer microbe as they move north

NEW NEIGHBORS As the Arctic emerges from a deep freeze, parasites including Sarcocystis pinnipedi (shown, purple) are able to infect animals that they have never encountered before.

M. Grigg

CHICAGO— Along with melting Arctic ice comes an erosion of natural barriers that once separated parasites from hosts.

That erosion has allowed at least two pathogens to infect marine mammals they were previously unknown in, said Michael Grigg, a molecular parasitologist at the National Institutes of Health in Bethesda, Md. He reported the findings February 13 at the annual meeting of the American Association for the Advancement of Science.

A newly identified parasite was once frozen safely away from grey seals (Halichoerus grypus). It has now infected some with disastrous consequences. In 2012, about 20 percent of healthy-looking grey seal pups born on Hay Island off the coast of Nova Scotia mysteriously died. The cause turned out to be a parasite that destroyed the livers of 404 pups and two adults, Grigg said.

Grigg and his colleagues found that the parasite, a microscopic creature shaped like a crescent moon, also infects about 80

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